Bus design parameter
1. Type : Dedicated or multiplexed
2. Arbitration : Centralized or distributed
3. Timing ; Synchronous or Asynchronus
4. Bus width ; Address or data
5. Data Transfer Type ; R, W, Read, Modify Write, after write, block
Bus Design Parameter in details
1. Bus Type :
i) Dedicated bus:
When a bus is permanently assigned only 1 functiion , it is called dedicated bus.
E.g. separate address and data lines separate bus for memory and I/O modules
Advantages: It gives high performance and less bus contention
Disadvantages : Increased size and cost.

ii) Multiplexed bus:
When the bus is used for more than 1 funcion in different time zones it is called multiplexed bus. E.g. 8085 microprocessor outputs A7- A0 in first clock cycles on pins. AD7 – AD0.
Advantages ; few pins lines are required . less cost and save space
Disadvantages: slow in speed
2. Bus Arbitration:
Several bus master connected to a common bus may require access to the same bus at the same time. A selection mechanism called bus arbitration describes which device should be given access to the bus

i) In Centralized approach; A hardware device called bus controller or bus arbiter allocates bus. It uses one of the following type
(1) Daisy chaining
(2) Polling
(3) Multiple priority levels

ii) In Distributed Approach: each master has arbiter compared to only single in centralized approach. Equal responsibility is given to all devices to carry out arbitration process, without using a central arbiter
3. Bus Timing: In synchronous timing ,e very event is synchronized by clock whereas in asynchronous every event occurring depends on previous events of bus .

4. Bus width: It decides the number of lines to be used for address and data. More addrss lines means more memory can be accessed e.g 16 line address make 2 16 = 64 kb , 20 address line makes 220 = 1 mb memory access .
More data lines means more number of bits can be transferred at a time. Therefore speed increases.
5. Data transfer type; A bus can support various type of data transfer
1) For multiplexed bus

a) Write operation : data is outputted immediately outputting address
b) Read operation: First address is outputted then sufficient acces s time is given gto address device to output data. Now data is read from bus
c) Read , modify write; Read data transfer is followed by write data transfer at the same address. It stop other cpu to use bus.
d) Read after write; Writer transfer is followed with read transfer after some access time . it is used for checking purpose.
e) Block operation; number of data are transferred at the same address one after another e.g. saving file in secondary storage.

2) For non-multiplexed bus :
Address and data outputted at the same time on different bus. It is faster system.